1. Field of the Invention
This invention relates to filtering systems, more particularly filtering systems used in storm drains.
2. Prior Art
Stormwater flows into storm drains, often located on or near a street or highway, and into under ground lines. A problem associated with stormwater run-off is contamination with heavy metals and hydrocarbons that have leaked onto the streets and highways from a variety of sources. Sediment contained in the stormwater run-off also creates problems. Many times the contamination is so high that the storm water discharge exceeds the pollution limits imposed by federal and state laws. Thus, a need exists for a water-filtering device that can filter out heavy metal and hydrocarbon contaminants.
Prior attempts have been made to design filtering systems placed below the surface of the drain within the drain basins. For example, U.S. Pat. No. 4,419,232 to Arntyr, et al discloses a two-tier system whereby a coarse material filter is placed above a finer filtering material. Arntyr, et al discloses that the filter bag disclosed therein is capable of filtering out oil and other viscous impurities from the drain water, but only to a certain extent. As noted by Arntyr, et al, the coarse filtering stage is necessary to prevent the filtering bag from breaking when filled with sticks, rocks, and other debris. U.S. Pat. Nos. 5,372,714 and 5,525,925 to Logue disclose the use of a subsurface filtering system whereby the filter is supported by a series of flaps which are sandwiched between the drain grating and a recess in the catch basin. The problems associated with this device are that the bag is susceptible to breaking for lack of support from below and that the flaps can become dislodged from between the basin recess and drain grating thereby causing the system to become inoperable. A further problem associated with the Logue device is the use of a woven polypropylene material. The woven material and lack of overflow outlets restrict the maximum flow rate through the system to about 40 gallons per minute per square foot and causes water flow to back up during heavy downpours, resulting in flooding around the drain. The use of a woven material also prevents the material from effectively filtering out the heavy metals and hydrocarbons. Thus, a need exists for a filter with increased flow capacity and the ability to filter out heavy metals and hydrocarbons.
One attempt to create a better storm drain liner is shown in applicant""s prior patents, U.S. Pat. No. 6,0867,583 and its continuation, hereby incorporated by reference. These devices generally show a basket with a bag liner place therein. The basket is attached to a frame and the frame is positioned in the inlet or can be attached to the storm drain. These patents also show one or more overflow flaps positioned in the bag liner near the top opening. The overflow flap is designed to allow excess incoming water to bypass the filter during periods of very heavy flow, that is, when the flow into the storm drain exceeds the filter""s throughput. The bypass flap allows fluids to enter the filter system but exit the system without passing through the filter medium: water flows between the sidewalls and the exterior of the filter to reach the outlet of the storm drain. Without the bypass flaps, the filter system could back up during periods of heavy flows.
The bypass flaps, however, can be ineffective. In periods of heavy flow when the bypass would be needed, the basket/filter below the bypass is fluid filled. These fluids generate outward pressures that can force the basket and filter into close engagement with the sidewalls of the storm drain. If this occurs, the bypass will be ineffectual, as the fluid flow path between the sidewalls of the drain and the exterior of the basket would be severely restricted or eliminated.
With the aforementioned considerations in mind, it is therefore an object of this invention to provide a single filtering system that is adaptable to all existing storm drains and has an effective by-pass means even when the basket/filter seals against the sidewalls of the storm drain.
An apparatus for a storm drain filter in a storm drain having an inlet and an outlet which comprises a basket positioned between said inlet and said outlet and a water-permeable filter positioned at least partially within said basket, the basket is attached to a frame for placement in the storm drain. Positioned in the basket is a riser tube, having an open top and open bottom. The open bottom penetrates the bottom of the basket.